1. Field of the Invention
This invention relates to the field of preventing contamination of a surface of a substrate during processing of the substrate.
2. Discussion of the Background
Surface contamination of substrates by particles is a serious problem at both atmospheric and sub-atmospheric pressures. Ultra-clean surfaces are desirable for processing in the microelectronics and optics industries. Particle contamination on wafer surfaces produces defects resulting in yield losses in the integrated circuit industry and reduced optical quality in the optics industry.
Even when extremely clean processing gases are used during surface processing, particles are generated due to the processing steps used for processing substrates. Those particles are usually less than 20 microns in diameter and typically less than 1 micron in diameter. Elimination of particles generated during processing steps, such as plasma deposition, plasma etching, and non-plasma processes, and identification and elimination of sources of particles produced by those processes are difficult.
Ultrasonic acoustic waves may be used to clean the substrate surface as disclosed in U.S. Pat. No. 5,090,432. However, that type of cleaning requires exposing a substrate surface to a liquid environment and that environment is incompatible with high vacuum process steps.
Electrostatic forces may be used to remove particles from a substrate surface as disclosed in U.S. Pat. No. 4,744,833. However, generation of electrostatic fields requires that the particles be charged and also interferes with processes depending upon application of a voltage to the substrate surface, such as sputtering and plasma etching processes.
Chemical reactions may be used to clean substrate surfaces, such as by removing an oxide layer from a semiconductor surface, but such cleaning processes can not selectively remove particulate deposited upon a substrate surface.
A need exists for in-situ processes which avoids contamination of a substrate surface by particles during processing.